The preparation of alumina by water hydrolysis of aluminum alkoxides is well-known. Alumina prepared by this process has many uses, such as catalyst for organic reactions, desiccant, and adsorbent. When subjected to certain calcination conditions the alumina is particularly useful as a catalyst for a variety of reactions.
A convenient way of preparing the aluminum alkoxides involves preparing a mixture of high-molecular-weight aluminum trialkyls by the Ziegler process. The aluminum trialkyls are then oxidized to the corresponding aluminum alkoxides.
A typical hydrolysis process is one wherein the water and aluminum alkoxides are fed continuously to a reactor. In the reactor two operations occur. First, the aluminum alkoxides are hydrolyzed, forming alumina and alcohols. Second, a phase split occurs between the water-alumina slurry and the alcohols. Subsequently, the alcohols and alumina-water phases are withdrawn from the reactor. The alumina-water slurry is subjected to further processing to eventually obtain the dried alumina, substantially free of alcohols.
We have found that high velocity injection of the aluminum alkoxides into the reactor results in an alumina product having improved physical properties. Unfortunately, this procedure destroys the alcohol-slurry (water-alumina) interface so that phase separation does not occur satisfactorily.
We have found that the advantages of high injection velocity can be attained by admixing the water and aluminum alkoxides under high velocity conditions prior to passing the resulting admixture to the reactor.